Optical mark recognition (OMR), also referred to as optical mark reading, is the process of capturing human-marked data from document forms such as surveys, tests, or other substrates bearing markings. One of the most familiar applications of optical mark recognition is the use of #2 pencil (HB in Europe) bubble optical answer sheets in multiple choice question examinations. Students mark their answers, or other personal information, by darkening circles marked on a pre-printed sheet. Afterwards the sheet is automatically graded by a scanning machine.
Many traditional OMR devices work with a dedicated scanner device that shines a beam of light onto the form paper. The contrasting reflectivity at predetermined positions on a page is then used to detect these marked areas because they reflect less light than the blank areas of the paper.
FIG. 1 shows an example of a test form 100 that may be used with OMR. The form 100 typically is a sheet of paper having various markings such areas 102, which can take on various colors such as red, blue, orange, green, black, or grey, and multiple choice answer receiving areas 106, each area having a label A, B, C, D, or E. The example form shown in FIG. 1 has 250 answer receiving areas formed as a matrix having 50 rows, with five answer receiving areas 106 per row. While taking a test, the test taker uses a writing instrument to make a mark, such as oval 104, in one of the desired answer receiving areas 106 corresponding to which answer (A, B, C, D, or E) the test taker believes is correct. Once completed, the form 100 is handed in to the test proctor and it is run through an OMR scanner, which reads the positions of the markings and compares them to a predetermined set of correct answers. In this manner, the test taker's test form 100 is graded.
FIG. 2 shows an example of a typical OMR scanner 200 having a form input tray 202, a form output tray 204, and a scanning head 206. The scanner 200 pulls one form at a time from the input tray 202 and runs it through the scanner pathway, and activating the scanning head 206 to scan for the presence and location of marks on the form. The presence of non-marked images on the form (e.g. background form marking) is not desirable to collect the OMR marks and ideally should be removed at scan-time. One technique to doing this is the use of Infrared (IR) light and marking the test with a graphite-based pencil. The scanner head 206 accomplishes this task by illuminating the form with infrared (IR) light, which causes the graphite-based pencil markings to appear opaque to the OMR sensor, while all other areas on the form (i.e., those areas not bearing graphite-based markings) are transparent to the sensor.